1. Field of the Invention
The present invention relates to a radiation tomographic image obtaining apparatus for obtaining tomographic images through radiation imaging.
2. Description of the Related Art
Mammography based on plain X-ray imaging is performed for breast cancer screening. Sensitivity of the mammography, however, is relatively low and the screening result is highly likely to be false positive. Consequently, diagnosis is performed by the plain X-ray imaging in the screening first, and if the screening result shows a possibility of breast cancer, another diagnosis using another modality (CT, MRI, or the like) is performed. Different modalities have different applications. For example, the mammography through plain X-ray imaging is used for detecting small calcifications and tumors. CT and MRI may obtain more amount of information and determine whether a detected tumor is benign or malignant. In mammography, a breast is squeezed while it is imaged. On the other hand, CT or MRI requires no breast compression. Thus, it is difficult to identify the corresponding positions between the mammography image and CT or MRI image, and therefore these images are unable to be used effectively in the diagnosis.
Consequently, researches have been conducted for a method of obtaining a breast tomographic image by tomosynthesis in which a plurality of radiation images are obtained by compressing a breast placed on a detector with a pressing plate and arcing an X-ray source with respect to the breast and detector, and a tomographic image is reconstructed on a plane parallel to the detection surface of the detector by translating the plurality of radiation images and adding the images after adjusting the sizes thereof.
The use of the tomosynthesis technique allows tomographic images sliced at an interval of, for example, 1.0 mm to be reconstructed. Further, boxel data including data samples Nx×Ny×Nz along X, Y, and Z axes respectively may be generated by reconstructing a plurality of tomographic images in the manner as described above. A method and system for generating a 3D image using the boxel data is proposed as described, for example, in U.S. Pat. No. 6,611,575.
Further, a system in which a 3D image is generated using an image reconstruction algorithm and visualized using a volume rendering mode or a cinema (motion image) mode is proposed as described, for example, in U.S. Patent Application Publication No. 20030194050.
A demand exists that, when performing a diagnostic observation, a detailed observation be allowed for a region of affected area, as well as all of the tomographic images obtained. Further, it is effective to make a comparison with an image obtained in the past, or, for pair organs like breasts, it is effective to make comparison between the right and left organs.
In view of the circumstances described above, it is an object of the present invention to provide a radiation tomographic image generation apparatus for generating tomographic images appropriate for diagnosis from radiation images obtained by tomosynthesis imaging. It is a further object of the present invention to provide a computer readable recording medium on which a program for causing a computer to perform functions of the apparatus.